where \(S=I+B^{2}.\) 
Since \(V\)  is selfadjoint, then due to Theorem 3 [1]} the operator \(V^{^{\!-\!1}}\)  is selfadjoint also.
Combining (REF ) with
Lemma 3 [2]}, we get that \(V^{^{\!-\!1}}\)  is strictly accretive.
Using these facts we can write
\(\Vert f\Vert  _{V^{^{ -\!1}}} \ge C\Vert f\Vert _{H } ,\,f\in \mathfrak {H}_{ V^{^{ -\!1}}} .\) 
